1. Field of the Invention
The present invention is directed to a device for monitoring tires, fastened to a vehicle wheel.
2. Discussion of the Background
Systems for the transmission of tire monitoring signals and devices for fastening them to a wheel are already known, but such conventional systems suffer from drawbacks.
U.S. Pat. No. 5,033,295 (Bosch) describes a system for detecting closing of a dual pressure contact from a modification of a reluctance of a secondary circuit, this modification of reluctance being perceptible by a tuned primary circuit. In this device, there is no transmission of energy in the secondary circuit. On the other hand, the exhibited device assumes a modification of the wheels by the addition of coils in the thickness of the wheel disks.
The "Tire Check" device of the company Technologie Sicurezza Stradale features a pressure sensor fastened to the wheel disk by two lugs tightened under two consecutive nuts, and connected to the inflation valve, and a radio transmitter connected to a receiver in the cab. Like the preceding device, this device does not transmit any activation energy to the sensor from the vehicle and relies on on-board batteries to assure the operation of the electrical elements. Furthermore, the method of mounting the lugs under the nuts of wheels exhibits the drawback of inducing considerable vibrations during tightening of the nuts with impact wrenches (factory tightening). These vibrations can damage possible electronics integral with these lugs.
The system developed by the Michelin company under the name "M.T.M.", for passenger vehicles, includes a mobile antenna mounted in the wheel disk, and a stationary antenna mounted on the caliper of the disk brake; this type of mounting could be done with wheels equipped with drum brakes only after having made considerable modifications to the production line elements that the wheels and drums are.
In the following text, by "hub" is meant the rotating hub of the wheel itself, as well as any other rotating element that is attached to it, such as a counting ring of an antilocking wheel (A.L.W.) system, rotating joint parts, etc.; and by "hub carrier" is meant the hub carrier of the wheel itself, as well as any other stationary element that is attached to it, such as an oil catcher, A.L.W. sensor support, etc. Also, by "wheel" is meant the unit including the two wheels fastened to one another during a mounting of dual tires as well as an ordinary wheel during a single tire mounting. Finally, by "wheel environment" is meant the unit including of the wheel, the hub, the hub carrier and the brake drum.